The invention is based on a device for detecting signals in an ignition system. The ignition system contains two ignition coils, and a capacitive signal coupling provided on the coils.
U.S. Pat. No. 4,795,979 discloses a device for determining the ignition pulse provided for a specific cylinder of an internal combustion engine. The ignition system contains a plurality of ignition coils, in each case two spark plugs being connected to the secondary windings of the ignition coils. This distributorless ignition system produces an ignition spark at each spark plug at each rotation of the internal combustion engine. In four-stroke internal combustion engines, the ignition sparks are accordingly produced both in the working stroke and in the discharge stroke. For diagnosing this ignition system, three capacitive signal output couplings are provided which are arranged on the ignition cables leading from the ignition coils to the spark plugs. The known device requires the ignition cables to be accessible so that the sensors can be attached. The extracted signals are fed into different signal evaluation circuits.
U.S. Pat No. 3,959,725 discloses the arrangement of a capacitive ignition voltage sensor on a distributor housing which, in addition to the distributor, also contains the ignition coil. The capacitive signal extraction is effected with an electrically conductive surface which is attached to the distributor in a suitable manner. This known device is designed for the diagnosis of a single-coil ignition system.